The invention relates to electrical power devices and methods of operation thereof, and more particularly, to uninterruptible power supply systems and methods of operation thereof.
Uninterruptible Power Supply (UPS) systems are power conversion systems that are commonly used to provide conditioned, reliable power for devices and systems such as computer networks, telecommunications networks, medical equipment and the like. UPS systems can provide temporary power to the devices and systems so that the devices and systems can continue to operate despite the loss of the primary power source and thereby can reduce the likelihood that valuable data may be lost.
UPS systems may provide uninterrupted power by switching from a primary power source to a secondary power source if loss of the primary power source is detected. When the primary power source is restored, the UPS system may switch from the secondary power source back to the primary power source. Similarly, the UPS system may switch from the primary power source to the secondary power source if the UPS system determines that the primary power source is inappropriate. For example, if a voltage level of the primary power source is less than a minimum acceptable level, the UPS system may provide uninterrupted power by switching from the primary power source to the secondary power source.
Conventional UPS systems can include separate modules that provide respective functions to provide the overall functions of the UPS system. For example, some conventional UPS systems include separate modules such as rectifiers, inverters, batteries, and switches that cooperate to provide the overall function of the UPS systems. Moreover, the separate modules may need to communicate to provide the overall UPS system functions. For example, in some of the scenarios described above, a rectifier module may need to communicate the condition of the power provided by the primary power source so that the UPS system can determine whether to switch to the secondary power source.
Unfortunately, in some conventional UPS systems, the interconnect used to provide communication between the separate modules may be expensive and difficult to manufacture or modify. For example, some conventional UPS systems use point-to-point wiring to connect the separate modules. Such a system may, use many separate wires to provide communications between the separate modules. Adding new modules may be difficult as new wiring may need to be added to connect the new modules to the existing modules.
In other conventional systems the modules may communicate over a network. Unfortunately, in many of these conventional systems some communications between modules may be problematic. In particular, in systems where modules can send identical communications the communications may conflict, which may result in less important communications being transmitted while more important communications are lost. Such systems are discussed further, for example, in U.S. Pat. No. 5,323,385 to Jurewicz et al. entitled Serial Bus Communication Method in a Refrigeration System. 
Furthermore, it may be desirable to place the UPS system and the system or device to which the UPS system provides power in separate locations. For example, the UPS system may be located in the basement of a building while the system (such as a mainframe computer system) is located on a different floor of the building. Unfortunately, in conventional UPS systems, monitoring the status of the UPS system from the system or device to which power is provided may be difficult. Accordingly, there is a need for improved communications in UPS systems.
The invention can provide improved methods, systems, and computer program products for communications in UPS systems over Controller Area Networks. In one embodiment of the invention, transmission of a first message is initiated at a first time according to a controller area network message frame format from a first module in the UPS system. The message is of a first type and includes first priority information in a separate priority field of a first controller area network message frame. Transmission of a second message is initiated at the first time according to the controller area network message frame format from a second module in the UPS system. The second message is of the first type and includes second priority information in the separate priority field of the second controller area network message frame. The first message is received by a third module if the first priority information is higher than the second priority information. Alternatively, the second message is received by the third module if the second priority information is higher than the first priority information.
The separate priority field can allow identical message types having different priority to be transmitted within the UPS system. For example, in a UPS system according to the invention, a rectifier off command can have higher priority than a rectifier reset command.
Accordingly, in a UPS system according to the invention wherein different modules issue commands to the same module, the more important commands can have priority over less important commands. For example, in a UPS system according to the invention, a rectifier off command can have higher priority than a rectifier reset command. Accordingly, in a UPS system according to the invention wherein different modules issue commands to the rectifier, the more important rectifier commands can have priority over less important rectifier commands.
In a further embodiment of the invention, the first and second messages include respective first and second module identifiers associated with the respective first and second modules. In particular, the CAN message format according to the invention also can include a separate module identifier field that uniquely describes the location of the module in the UPS system which transmitted the CAN message. For example, the module identifier can be provided by customized wiring in a wiring harness connected to an associated communications interface circuit. Each communications interface circuit can determine its location in the UPS system based on the specific wiring provided to the communications interface circuit by the wiring harness. Accordingly, each module in the UPS system can format the CAN message with its associated unique module identifier thereby enabling the UPS system to resolve CAN access conflicts in situations where modules transmit identical messages having the same priority at the same time.
In another embodiment of the invention, the first message includes destination routing information in a separate destination routing field of the controller area network message frame, the destination routing information identifies a bridge module in the first UPS system that electrically couples the first UPS system to a second UPS system. Accordingly, the first message is received at the bridge and relayed to second UPS system. The separate destination routing field can be used to transmit commands to a bridge in the UPS system. In particular, the bridges can be identified by a bridge ID. In operation, a command can be transmitted to another UPS system via a respective bridge by including the bridge identifier of the bridge which connects the two UPS systems in the separate destination routing field.
In another embodiment of the invention, the first message includes a first data field associated with a category of data included in the first message and a second data field associated with a sub-category of data included in the category of data. In particular, bytes of data field can be organized as categories and subcategories that describe the types of data included in the data field and subcategories wherein each subcategory is a type of data associated with a particular category. For example, the value of byte 0 of the data field can indicate the category in which the data is included and byte 1 can identify the subcategory in which the data in included. Data bytes 2 through 7 can be the data identified by the category and subcategory identifiers. The categories of the data can allow the data to be organized in a hierarchical fashion, thereby providing improved organization for system design and debug.